Integrated flow controller module

ABSTRACT

A flow controller module comprising at least one micro flow sensor and a microvalve, integrated in a micro flow channel, is disclosed. The micro flow sensor comprises a pressure sensitive flow sensor. At the position of the micro flow sensor, the micro flow channel is provided with an orifice so that pressure of a flow may be enlarged to facilitate measurement of the flow speed. The microvalve comprises a silicon microbridge with a mesa structure and is driven by a voltage. The microvalve may operate under a normally closed mode or a normally open mode. Disclosed in this invention is also a flow sensor suited in the integrated flow controller module. Methods for preparing the flow sensor and the flow controller module are also disclosed.

FIELD OF THE INVENTION

The present invention relates to an integrated flow controller module,especially to an integrated flow sensor module comprising a pressuresensitive flow sensor.

BACKGROUND OF THE INVENTION

Due to the developments in the micro machining technology, a micro flowcontroller module comprising a plurality of sensors, actuators andcontrol circuits may be integrated in one single dice. An integratedmicro flow controller prepared with the micro machining technology iscapable of measuring and controlling flows within a microchannel. Whenthe flow to be measured and controlled is a gaseous flow, the applicablevelocity may be under 1/min. For a liquid flow, the applicable velocitymay be at the scale of μ1/min. The geometric scale of a flow controlleris centimeter. The advantages of the integrated micro flow controllerinclude energy saving, short response time and compactness. Micro flowcontrollers may further be associated in matrix to precisely controlflows in a larger scale.

A micro flow controller module generally includes a flow sensor tomeasure the velocity of a flow, a microvalve to control the velocity anda system controller circuit to control the operation of the microvalve.In the conventional art, the microvalve may be an electromagnetic or apiezoelectric valve. The flow sensor may be a wicked thermal flowsensor. Due to the numbers and volumes of the components, volume of amicro flow controller is always bulky. In addition, these componentsmust be prepared and assembled under superfine processes and packagedmechanically. As a result, manufacture costs of the micro flowcontroller may not be reduced.

It is thus a need in the industry to have an integrated flow controllerwhere a flow sensor and a microvalve are integrated in one single dice.It is also a need to have a compact flow controller module that may beprepared under the semiconductor manufacture process.

OBJECTIVES OF THE INVENTION

The purpose of this invention is to provide an integrated flowcontroller module where a flow sensor and a microvalve are integrated inone single dice.

Another purpose of this invention is to provide an integrated flowcontroller module that may be prepared under the semiconductormanufacture process.

Another purpose of this invention is to provide a simplified, compactand reliable micro flow controller module.

Another purpose of this invention is to provide an integrated micro flowcontroller module comprising a pressure sensitive flow sensor.

Another purpose of this invention is to provide a micro flow sensorsuited in the above integrated flow controller modules.

Another purpose of this invention is to provide methods for thepreparation of the above integrated micro flow controller module and itsmicro flow sensors.

SUMMARY OF THE INVENTION

According to the present invention, an integrated flow controller modulecomprising at least one micro flow sensor and a microvalve is disclosed.The micro flow sensor and the microvalve are integrated in a micro flowchannel. The micro flow sensor comprises a pressure sensitive flowsensor. The micro flow channel is provided with an orifice adjacent tothe flow sensor to enlarge the pressure of a flow to be measured. Themicrovalve comprises a silicon microbridge with a mesa structure and isdriven by a voltage. The microvalve may operate under a normally closedmode or a normally open mode.

These and other objectives and purposes may be clearly understood fromthe detailed description of the invention by referring to the followingdrawings.

IN THE DRAWINGS

FIG. 1 illustrates the sectional view of the first embodiment of theintegrated flow controller module of the invention.

FIG. 2 illustrates the flow chart for the preparation of the integratedflow controller module of FIG. 1.

FIG. 3 illustrates the sectional view of the second embodiment of theintegrated flow controller module of the invention.

FIG. 4 illustrates the sectional view of the third embodiment of theintegrated flow controller module of the invention.

FIG. 5 illustrates the sectional view of the fourth embodiment of theintegrated flow controller module of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The integrated flow controller module of this invention comprises a flowchannel, a proportional microvalve and a flow sensor, all integrated inone single dice. A fluid may be introduced into the flow channel from aninlet. A pressure sensitive flow sensor comprising a pressure sensitiveresistor or a pressure sensitive capacitor is positioned at a measuringarea of the flow channel. An orifice is preferably provided at themeasuring area of the flow channel. In some embodiments of thisinvention, a flow controller module has more than one flow sensor andcorresponding number of orifices. Velocity of the fluid flow is measuredat the measuring area(s) and the velocity is converted into an electricsignal. The fluid is then introduced into a microvalve area providedwith a microvalve. The microvalve comprises a silicon microbridge with amesa structure and operates under a normally closed mode or a normallyopen mode. A controller controls the operations of the microvalve basedon the velocity of the fluid flow.

Description of the embodiments of the integrated flow controller modulewill be given in the followings.

Embodiment 1

FIG. 1 illustrates the sectional view of the first embodiment of theintegrated flow controller module of the invention. As shown in thisfigure, the integrated flow controller module of this embodiment has athree-layer structure. Among them, the upper layer 1 is prepared with asilicon material, or any other suited material. The upper layer 1comprises 3 cavities: first pressure cavity 11 and second pressurecavity 12 respectively provide pressure adjustments P1 and P2 to adjustthe pressure of the flow to be measured and controlled. Values of thepressure adjustments P1 and P2 may be decided according to themeasurable scope of the velocity, such that the measurable scope of thevelocity may be wide. The third pressure cavity 13 provides pressureadjustment P3 to microvalve (to be described hereinafter), so that theapplicable velocities of the flow controller may be adjusted.

The middle layer 2 comprises a measuring area and a microvalve area.Material for the middle layer 2 may be silicon or other suitedmaterials. Orifices 21 and 22 are provided at positions corresponding tothe first pressure cavity 11 and the second pressure cavity 12,respectively. Although it is not intended to limit the scope of thisinvention, the purpose of the orifices 21 and 22 is to enlarge pressuredifferences of the flow so to improve the precision of measurement.Cavities 23 and 24 are provided beneath the third pressure cavity 13.Between cavities 23 and 24 is a mesa structure 25 to function as amicrovalve. In the embodiments of this invention, the mesa structure 25is the non-etched area of the middle layer 2. In other embodiments, themesa structure 25 is prepared separately.

Between the upper layer 1 and the middle layer 2 is an EPI layer 4. TheEPI layer 4 functions as a membrane to provide elastic sustention inresponse to pressure of the flow. 4 impurity layers 41a, 41b, 41c and41d are formed under first and second pressure cavities 11 and 12,respectively, to function as pressure-sensitive resistors. Coupling withsaid resistors 41a, 41b, 41c and 41d are electrodes 43a, 43b, 44a and44b. When variations of fluid pressure occur in orifices 21 and 22,voltages of electrodes 43a, 43b, 44a and 44b will vary due to variationsin resistance at resistors 41a, 41b, 41c and 41d. With this, velocity ofthe flow may be measured by a microprocessor (not shown) according tothe conventional technology.

In this figure, two orifices are used to generate flow pressure signalsso that the signals may be calibrated. It is however possible to useonly one or more than two orifices to generate flow pressure signals.

The above may be thus called a "measuring area", since velocity of theflow is measured in this area.

In the other side of the middle layer 2 is a microvalve area. Betweenthe mesa structure 25 and the third pressure cavity 13 is also an EPImembrane 4. The EPI membrane in the microvalve area may be thecontinuation of that in the measuring area. Preferably, an insulator 47is provided between these two sections. Above the mesa structure 25, animpurity layer 45 is formed on the EPI membrane 4. Coupling with theimpurity layer 45 are electrodes 46a and 46b. The pattern of theimpurity layer 45 may be tortuous, circular or other suited patterns.The EPI membrane 4 provides an elastic sustention to support the mesastructure 25. When an external voltage is applied to electrodes 46a and46b, thermal dissipation will occur in impurity layer 45 so that EPImembrane 4 will be deformed and bend upward. Because of this drivingforce, the mesa structure 25 is moved upward such that its bottom doesnot butt against the lower layer 3. An opening between the mesastructure 25 and the lower layer 3 allows fluid to flow through.

As the upward movement of the mesa structure 25 is in a proportionalrelation with the voltage supplied to electrode 46a and 46b, thevelocity of the flow may thus be controlled. The mesa structure 25 thusfunctions as a microvalve. Other microvalves that controls fluidvelocities by an active driving force and may be integrated with a flowsensor in one single dice may also be applicable in this invention.

The lower layer 3 comprises an inlet, an outlet and a channel for a theflow to be measured and controlled. In this embodiment, lower layer 3 ismade of silicon material. Other material may also be used to prepare thelower layer 3. In lower layer 3, 31 is a flow inlet, 32 is entrance forthe first orifice 21, 33 is connection channel between first and secondorifice 21 and 22, 34 is connection channel between second orifice 22and cavity 23, 35 is outlet of the channel. Two extruders 36, 36 areprovided at outlet 35 to ensure the blockage of the flow by the mesastructure 25. Extruders 36, 36 may be prepared with a material same asthat of lower layer 3. Other materials may also be used to prepareextruders 36, 36.

Preparation of the integrated flow controller module of this embodimentwill be given in the followings. FIG. 2 illustrates the flow chart forthe preparation of the integrated flow controller module of FIG. 1. Asshown in this figure, in the preparation of a micro flow controller, asilicon substrate is prepared at 201 as the lower layer 3. At 202 etchthe substrate 3 to form an inlet 31, an outlet 35, entrance 32,connection channels 33 and 34, and extruders 36, 36.

At 203 a sacrificial layer (not shown) is formed on the substrate 3. At204 a middle layer 2 is formed on the sacrificial layer 2. At 205, etchthe assembly to form a first orifice 21, a second orifice 22 andcavities 23 and 24, while a mesa structure 25 is reserved. During theetching, areas of the sacrificial layer above inlet 31, entrance 32,connection channels 33 and 34 and outlet 35, shall be etched off so thatthe channel is formed.

Thereafter, at 206 an EPI layer 4 is formed on the middle layer 2. At207 impurities are planted into the EPI layer 4 to form impurity layers41a, 41b, 42a, 42b and 45. If necessary, at 208 an insulator 47 isprepared in the EPI layer 4, between the measuring area and themicrovalve area.

Later, at 209 electrodes 43a, 43b, 44a, 44b and 46, 46 are bonded ontopurity layers 41a, 41b, 42a, 42b and 45. Suited materials for electrodesinclude aluminum, molybdenum, tungsten or other suited metal or metalalloys. The electrodes may be evaporated or bonded. At 210 an upperlayer 1 is formed on the EPI layer 4. Suited materials for the upperlayer 1 include silicon, glass or high molecular materials. At 211 afirst pressure cavity 11, a second pressure cavity 22 and a thirdpressure cavity 23 are formed in the upper layer 1 by etching the upperlayer 1. Finally, at 212, a coating layer (not shown) is formed on theupper layer 1 and an integrated flow controller module is accomplished.Here, material of the coating layer may be the same as that of the upperlayer.

In the preparation of the upper layer 1, the cavities 11, 12 and 13 maybe etched through a sacrificial layer. The upper layer 1 may also beprepared with cavities 11, 12 and 13, and then bonded to the EPI layer4.

When the integrated micro flow sensor is applied to control the velocityof a fluid, the fluid is introduced into the first orifice 21 throughinlet 31 and entrance 32. The fluid then enters the second orifice 22through connection channel 33. Pressure of the fluid is transferred toimpurity layers 41a, 41b, 42a and 42b so that resistance values ofimpurity layers 41a, 41b, 42a and 42b vary. In this embodiment, EPIlayer 4 is N pole and electrodes 43a, 43b, 44a and 44b are connected inparallel. Variations of voltage at electrodes 43a, 43b, 44a and 44b aremeasured by a microprocessor (not shown) and velocity of the flow isobtained. Any conventional art may be applied to convert the voltagevariations into velocity of the fluid flow. Description thereof is thusomitted.

While the velocity of the flow is measured, microprocessor generatesvelocity control signals according to a predetermine regulation, andoutputs the signals to electrode 46, 46. Thermal dissipation occurred inimpurity layer 45 drives EPI layer 4 to bend upward so that mesastructure 36 is moved upward for a certain distance. An opening betweenthe mesa structure 36 and the lower layer 3 allows the fluid to flow tooutlet 35. The sectional area of the opening may be decided by thevoltage supplied to electrodes 46, 46.

Embodiment 2

FIG. 3 illustrates the sectional view of the second embodiment of theintegrated flow controller module of the invention. In this figure,components that are same in FIG. 1 are labeled with same numbers. Asshown in this figure, the flow controller module of this embodimentcomprises a microvalve operating in a normally open mode. In otherwords, recessions 35a, 35a are provided in lower layer 3 at areasadjacent to mesa structure 25 such that mesa structure 25 does not buttagainst lower layer 3 under the initial status. When a voltage isapplied to electrodes 46, 46 EPI layer 21 will generate a deformationand moves mesa structure 25 downwards. The sectional area of the openingbetween mesa structure 25 and lower layer 3 will vary according to thevoltage applied, such that the velocity of the fluid flow may becontrolled.

The preparation and the operation of the integrated micro flowcontroller module of this embodiment are similar to that ofembodiment 1. Detailed description thereof is then omitted.

Embodiment 3

FIG. 4 illustrates the sectional view of the third embodiment of theintegrated flow controller module of the invention. In this figure,components that are same in FIG. 1 are labeled with same numbers. Asshown in this figure, the flow controller module of this embodiment hasa substantially similar structure of that of embodiments 1 and 2, exceptthat no impurity layers are formed on the EPI layer 4, under pressurecavities 11 and 12. Instead, at the ceilings of the pressure cavities 11and 12 provided are electrodes 14 and 15 respectively. Electrodes 14 and43a, 43b and electrodes 15 and 44a, 44b jointly and respectivelyfunction as capacitors.

When a fluid is introduced into orifices 21 and 22, pressure of thefluid forces EPI layer 4 to deform, such that capacitance of thecapacitors varies due to variations in distance between electrodesconsisting the capacitors. If EPI layer 4 is connected to P pole, andelectrodes 14 and 15 to N pole, capacitance of the capacitors may bemeasured and converted into velocity of the flow by a microprocessor(not shown). Conversions from capacitance into velocity may be performedaccording to any known formula. The microprocessor then controls theoperations of the microvalve in a way similar to that of theabove-mentioned embodiments. Description thereof is thus omitted.

As to the preparation of the integrated flow controller module of thisembodiment, electrodes 14 and 15 may be formed on the ceilings of thepressure cavities 11 and 12. They may be bonded to the upper layer 1after pressure cavities 11, 12 and 13 are formed. They may also bebonded to the upper layer 1 before a sacrificial layer (not shown) isformed on upper layer 1. Suited materials for electrodes 14 and 15include platinum and other metal or metal alloys.

Embodiment 4

FIG. 5 illustrates the sectional view of the fourth embodiment of theintegrated flow controller module of the invention. In this figure,components that are same in FIG. 1 are labeled with same numbers. Asshown in this figure, the flow controller module of this embodiment isnot provided with an upper layer, and thus the pressure cavities.Electrodes 43a, 43b, 44a, 44b and 46 are exposed to the external of thestructure. In some embodiments, a coating layer covers these electrodes.

Since no pressure cavities are provided, the applicable velocity of theflow controller module of this embodiment will be limited by thecharacter of the EPI layer 4.

The flow controller module of this embodiment may operate under anormally opened mode or under a normally closed mode. Preparation andoperation of the embodiment are similar to that of the precedingembodiments. Description thereof is then omitted.

Embodiments 5

In embodiments 1, 2 and 4, if no microvalve area is provided and outlet35 is formed under connection channel 34, the assembly may function as amicro flow sensor. Here, the microprocessor (not shown) converts thepressure of the fluid into velocity values and outputs such velocity.

Embodiment 6

In embodiment 3, if no microvalve area is provided and outlet 35 isformed under connection channel 34, the assembly may function as a microflow sensor. Here, the microprocessor (not shown) converts variations incapacitance of the capacitors into velocity values and outputs suchvelocity.

Effects of the Invention

In the integrated flow controller module of this invention, the flowsensor(s), the actively driven microvalve and the microchannel areintegrated in one single dice. The module may be prepared in a largequantity under a known semiconductor manufacture process. The module soprepared is compact and easy to prepare. Since the components are notprepared separately and the flow sensors are position directly in thefluid channel, the structure and the manufacture process are furthersimplified and its volume is further reduced.

As the present invention has been shown and described with reference topreferred embodiments thereof, those skilled in the art will recognizethat the above and other changes may be made therein without departingfrom the spirit and scope of the invention.

What is claimed is:
 1. An integrated flow controller module comprising:afluid channel allowing a fluid to flow through; a flow sensor providedin said fluid channel to measure velocity of said flow; a microvalveassembly positioned in said fluid channel to control velocity of saidflow; and a controller to generate microvalve assembly control signalsaccording to velocity of said flow; wherein said flow sensor comprises:apressure sensor to measure pressure of said fluid; and a pressure signalgenerator to convert pressures measured by said pressure sensor into anelectric format and to output pressure signals of said pressures; andwherein said microvalve assembly comprises:a microvalve to controlsectional area of said fluid channel; and a microvalve controller tocontrol operations of said microvalve according to said microvalveassembly signals; characterized in that said microvalve is elasticallysustained by a wall of said fluid channel and that said microvalvecontroller controls operations of said microvalve by generating heat tosaid wall such that deformation of said wall occurs.
 2. The integratedflow controller module according to claim 1 wherein said microvalvecomprises a semiconductor mesa structure inside said fluid channel; saidwall sustaining said microvalve comprises an elastic semiconductormembrane; and said microvalve controller comprises a resistor layer onsaid wall, adjacent to said mesa structure and at least one electrodeadjacent to said resistor layer; whereby deformation of said wall iscaused by applying a voltage to said at least one electrode.
 3. Theintegrated flow controller module according to claim 1 or 2 wherein saidfluid channel comprises an elastic wall element; said pressure sensorcomprises a resistor layer on said elastic wall element; and saidpressure signal generator comprises at least one electrode adjacent tosaid resistor layer.
 4. The integrated flow controller module accordingto claim 3 further comprising an orifice in said fluid channel adjacentto said pressure sensor and a closed pressure cavity external to saidelastic wall, adjacent to said resistor layer.
 5. The integrated flowcontroller module according to claim 4 wherein said orifice comprises astopper.
 6. The integrated flow controller module according to claim 3wherein said elastic semiconductor membrane and said elastic wallelement are connected.
 7. The integrated flow controller moduleaccording to claim 3 wherein said elastic semiconductor membrane andsaid elastic element are isolated with an insulator.
 8. The integratedflow controller module according to claim 1 or 2 wherein said microvalveis a normally closed valve.
 9. The integrated flow controller moduleaccording to claim 1 or 2 wherein said microvalve is a normally openedvalve.
 10. The integrated flow controller module according to claim 1 or2 wherein said fluid channel comprises an elastic wall element; saidpressure sensor comprises a first electrode on said elastic wallelement, a closed space surrounding said first electrode and a secondelectrode on said closed space at an opposite position to said firstelectrode.
 11. The integrated flow controller module according to claim10 further comprising an orifice in said fluid channel adjacent to saidpressure sensor.
 12. The integrated flow controller module according toclaim 11 wherein said orifice comprises a stopper.
 13. The integratedflow controller module according to claim 10 wherein said microvalve isa normally closed valve.
 14. The integrated flow controller moduleaccording to claim 10 wherein said microvalve is a normally openedvalve.
 15. The integrated flow controller module according to claim 10wherein said elastic semiconductor membrane and said elastic wallelement are connected.
 16. The integrated flow controller moduleaccording to claim 10 wherein said elastic semiconductor membrane andsaid elastic wall element are isolated with an insulator.